Cross directional zoned bicomponent films, film laminates, and systems and methods for manufacture of the same

ABSTRACT

Coextruded films provide cross directional zoned multiple components side-by-side to one another. Systems and methods relate to coextruding such films. During coextrusion, a first polymer conjoins with a second polymer while a temperature differential is maintained between the first and second polymers. This temperature differential is selected to reduce a difference between the viscosities of the first and second polymers making the viscosity of the first polymer close enough to the viscosity of the second polymer to avoid separation upon coextrusion. Further, the films may form a layer in subsequent lamination to other material layers.

BACKGROUND OF THE INVENTION

Coextrusion of two or more different polymers or polymer compositionsenables forming composite sheet or film products that have componentsdefined by distinct layers or zones corresponding to each materialextruded. Depending on how the compositions are extruded, each materialmay be laminated one on top of another across the film and/or bedisposed across the film side-by-side to one another. Some coextrusiontechniques include independent temperature control associated with thedifferent polymers in order to accommodate layers having thermallydistinct processing requirements or equalize layer thickness when eachmaterial is laminated one on top of another across the film. Anotherissue that arises in particular with respect to side-by-side interfacingof the polymers in the film involves mechanical stability where thedifferent polymers connect. When the different polymers areside-by-side, edge seams provide relatively less surface area toestablish lamination than if the polymers are laminated one on top ofanother across the film.

The films in which the different polymers are edge laminated requireselection of the different polymers to ensure compatibility duringprocessing. If the different polymers lack compatibility, the componentsseparate upon extrusion and fail to form a unified film inclusive ofeach region of the different polymers across the film. This requirementplaces an undesirable limitation on what polymers may be chosen.Compatibility needs thus dictate the different polymers that can beeffectively used, thereby limiting or preventing selection of thedifferent polymers based on other criteria such as costs, physicalcharacteristics or other properties of actual commercial interest.

Therefore, there exists a need for improved cross directional zonedmultiple component films, laminates utilizing the films, and systems andmethods of coextruding the films.

SUMMARY OF THE INVENTION

In one embodiment, a method of coextruding polymers into an edgelaminated film includes supplying a first polymer melt stream at a firsttemperature to a first inlet of a coextruder body and supplying a secondpolymer melt stream at a second temperature different than the firsttemperature to a second inlet of the coextruder body. Further, themethod includes directing the first and second melt streams throughfirst and second flow passageways passing through the body to aconverged output of the streams, wherein the first flow passagewayincludes a transverse diverging chamber laterally oriented relative tothe second flow passageway at the converged output. Outputting theconverged output from the body forms the edge laminated film continuousacross a full width of the film.

For one embodiment, an extrusion system for coextruding polymers intoedge laminated films includes a coextruder body having an outputconverged from first and second flow passageways passing through thebody to respectively first and second inlets, wherein the first flowpassageway includes a transverse diverging chamber laterally orientedrelative to a portion of the second flow passageway preceding theoutput. A first melt stream input couples to the first inlet, and asecond melt stream input couples to the second inlet. The second meltstream input is thermally isolated from the first melt stream input andcontrollable to a different temperature than the first melt streaminput.

According to one embodiment, an edge laminated film includes a firstpolymer shaped in a planar form. The planar form is continuouslyextended by a second polymer laminated along an edge of the firstpolymer as defined by a thickness of the planar form. The first polymerhas a viscosity versus temperature curve, as measured at shear rates of500 1/s, 1000 1/s and 1500 1/s, at least 10 percent different than thesecond polymer throughout a melt temperature range of each of thepolymers, wherein the viscosity is determined by a capillary rheometerequipped with a 1 mm die utilizing a 10:1 length to diameter ratio and a60° entrance angle. The melt temperature ranges are defined as a minimuminitial softening temperature for a respective one of the polymers to amaximum of 25-50° C. less than a decomposition peak, as determined by adifferential scanning calorimetry (DSC) curve obtained for a 5.5 mgsample of the respective one of the polymers heated at 20° C./minute andcooled at 10° C./minute in the presence of either nitrogen or oxygen.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of theembodiments can be understood in detail, a more particular descriptionof the embodiments, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a top view of a system for coextruding different polymers intoan edge laminated film, according to an embodiment.

FIG. 2 is a side view of the system taken across line 2-2 in FIG. 1 andillustrating separate feeds into a coextruder of the system, accordingto an embodiment.

FIG. 3 is a view of a die body first section of the coextruder,according to an embodiment.

FIG. 4 is a front view of the coextruder outputting the edge laminatedfilm, according to an embodiment.

FIG. 5 is a side view of the coextruder outputting the edge laminatedfilm that is subsequently laminated between two additional materiallayers, according to an embodiment.

FIG. 6 is a partial front view of the coextruder outputting separatefilms with each film being mono-component based on respective first andsecond polymers processed without viscosity manipulation.

FIG. 7 is a partial front view of the coextruder outputting the edgelaminated film, as identified in FIG. 4, made with the first polymer andthe second polymer shown in FIG. 6 but processed with viscositymanipulation.

DETAILED DESCRIPTION

Embodiments relate to coextrusion of two or more materials that havedisparate viscosities at one common melt temperature but are processedat different temperatures during the coextrusion. The materials mayinclude two different polymers extruded side-by-side such thatlamination occurs along an edge seam bisecting a thickness of the filmand extending in a “machine direction.” As used herein, the term“machine direction” or “MD” refers to length of the film in thedirection in which the film is produced. The term “cross machinedirection” or “CD” means the width of film, i.e., a longest dimension ofthe film in a direction generally perpendicular to the MD. For example,a first polymer may be maintained in a first portion of the width of thefilm and a second polymer may be maintained distinct from the firstportion in a second portion of the width of the film. In someembodiments, multiple edge laminations between polymers may form CDzones that provide multiple stripes of the polymers across the film atany interval in the CD. The edge lamination may occur within a centralregion of the film and not necessarily at or toward CD sides of thefilm.

FIG. 1 illustrates a system 100 for coextruding different polymers intoan edge laminated film, according to one embodiment. The system 100includes a coextruder 102 supplied with first and second polymers 104,106 (represented by arrows) distributed via, respectively, first andsecond conduits 105, 107. The second conduit 107 contains the secondpolymer 106 melted and flowing out from an extruder 108 prior tobranching of the second conduit 107 to enable coupling to first andsecond inputs 112, 114 into the coextruder 102. The first and secondinputs 112, 114 at spaced apart locations along the coextruder 102 maycoincide with approximate locations where the second polymer 106 isoutput when making the film. This arrangement may serve to limit dwelltime of the second polymer 106 in the coextruder 102, for reasonsexplained further herein. To this end, position and number of separatestreams of the second polymer 106 entering the coextruder 102 thoughindividual inputs, e.g., the first and second inputs 112, 114, may varyfor particular applications and may depend on quantity and location ofstripes in the film formed by the second polymer 107. While someembodiments may utilize a common melt pump for two or more inputs, afirst melt pump 113 in communication with the first input 112 along witha second melt pump 115 in communication with the second input 112independently control urging of the second polymer 106 into thecoextruder 102. Corresponding motors 116 couple through respective gearboxes 118 to power the first and second pumps 113, 115. Second conduitheaters 110 maintain the second polymer 106 at an identified secondtemperature upon exiting the extruder 108.

A similar arrangement as described with respect to the second polymer106 may provide extrusion and pumping of the first polymer 104 into thecoextruder 102. The first conduit 105 couples, for example, to a singlecentral input 120 of the coextruder 102, but may couple to a pluralityof additional inputs or at another location depending on, for example,placement of the first polymer 104 across the film that is produced.Desirably, first conduit heaters 122 maintain the first polymer 104 atan identified first temperature, which is different than the secondtemperature, prior to entry into the coextruder 102. For someembodiments, heating of the coextruder 102 to about the firsttemperature establishes a first thermal zone A of the system 100isolated and different than a second thermal zone B of the system 100.Thus, the second thermal zone B corresponds to supply of the secondpolymer 106 to the coextruder 102 while temperature of the first polymer104 is associated with the first thermal zone A.

A controller 124 regulates heating of the system 100 to achieve a giventhermal differentiation between the zones A, B. To this end, thecontroller 124 is programmed with, or programmable with, one or moretemperature set points for various components of the system 100. Thecontroller 124 may be a general-purpose computer (e.g., a workstationfunctioning under the control of an operating system) or aspecial-purpose programmable device such as a programmable logiccontroller (PLC). In operation, the controller 124 sends appropriatecontrol signals along transmission lines or pathways 126 to, forexample, the extruder 108, the first and second conduit heaters 122,110, and the coextruder 102 to adjust heating thereof in order to obtainthe temperature set points as predetermined. For some embodiments, thecontroller 124 provides the first thermal zone A with melt temperatureat least 25° C., or at least 50° C., or at least 100° C., different thanthe second thermal zone B.

Since polymers are generally poor conductors, the second polymer 106passes through the coextruder 102 without a substantial temperaturechange toward the first temperature of the coextruder 102 from thesecond temperature of the second polymer 106 when introduced into thecoextruder 102. Further, limiting path length and hence dwell time ofthe second polymer 106 within the coextruder aids in decreasing thermalinfluence of the coextruder 102 on temperature of the second polymer106. The first polymer 104 thus conjoins with the second polymer 106while a temperature differential is retained between the first andsecond polymers 104, 106. This temperature differential, which may beabout 50° C., is selected to substantially match viscosities of thefirst and second polymers 104, 106 at the point where the first andsecond polymers are conjoined. For some embodiments, zoned heatingand/or insulating within the coextruder 102 may at least facilitateestablishing the temperature difference between the first and secondpolymers 104, 106. Since temperature differentials as defined herein arebased on melt temperatures, the melt temperature of the first and secondpolymers 104, 106 refers to bulk temp of the respective polymer stream,at the corresponding inputs 112, 114, 120 to the coextruder 102, astaken by a typical melt probe thermocouple.

Criteria for selecting the temperature set points include achievingidentified temperatures that are within corresponding processing melttemperature ranges for each of the first and second polymers 104, 106and that reduce a difference between viscosities of the first and secondpolymers 104, 106. Reducing the difference between the viscosities ofthe first and second polymers 104, 106 makes the viscosity of the firstpolymer 104 close enough to the viscosity of the second polymer 106 toavoid separation (see, FIG. 6 described in more detail below) uponcoextrusion. For some embodiments, establishing close proximity inviscosities between the first and second polymers 104, 106 refers toobtaining less than a 50 pascal-second difference between theviscosities that may otherwise differ by at least 50 pascal-secondthroughout a common (i.e., no independent and different temperaturecontrol of the first and second polymers 104, 106) melt temperaturerange of the first and second polymers 104, 106. In one embodiment,matching of viscosities is achieved at the shear rate of the processingorifice, which as shown is a slot of the coextruder 102 through whichthe polymers 104, 106 exit. In some embodiments, matched viscositiesbetween the first and second polymers 104, 106 constitute viscositieswithin about 5 percent, about 10 percent, about 15 percent, or about 20percent of one another while unmatched viscosities (i.e., without melttemperature control described herein) are not within about 5 percent,about 10 percent, about 15 percent, or about 20 percent of one another.For example, if one viscosity is 100 pascal-second then that viscosityand another viscosity are within 10 percent of one another if the otherviscosity is anywhere between 90 pascal-second and 110 pascal-second.

As used herein, shear rate is calculated as 6*Q/(W*H²) where Q is flowrate (cubic centimeters per second; cc/sec), W is die wet width(centimeter; cm) that corresponds to the CD dimension of the film 400 atthe extruder 102 (see, FIG. 4), and H is die gap (cm) that correspondsto thickness of the film 400 at the extruder 102 (see, FIG. 5). The flowrate may be calculated from the pump rate(s) and densities of the firstand second polymers 104, 106 at respective temperatures in the die gap.By way of example for one processing criteria, the shear rate is 10621/s given a die wet width of 226 cm, a die gap of 0.0813 cm, anapproximated melt density of 0.95 g/cc, and a pump rate of 251 g/s.Based on the foregoing, a different shear rate may exist for eachpolymer, such as occurs if the throughput and/or density of the firstand second polymers 104, 106 are different, and may necessitateappropriate temperature process control. Since shear rate changes withthroughput, and some polymers may be more sensitive to the change inthroughput than others, a compensatory temperature change to one or bothof the first and second polymers 104, 106 may be associated with thethroughput change.

FIG. 2 shows a side view of the coextruder 102 having die body first andsecond sections 200, 202 mated together. An exemplary heating cartridge204 along with others embedded into the first and second sections 200,202 enable manipulating the temperature of the coextruder 102 to, forexample, the first temperature. The die body first section 200 mayinclude a die bolt assembly 206 across the CD of the coextruder 102 toprovide lip adjustments for controlling thickness of the film produced.

Matching recesses formed on the die body first and second sections 200,202 may define along an interface between the sections 200, 202 a firstpolymer melt stream pathway 208, a CD spreading manifold 210, a preland212 and a land 214. The first polymer melt stream pathway 208 fluidlyconnects the central input 120 for the first polymer 104 with the CDspreading manifold 210. Porting through the die body second section 202defines a second polymer melt stream pathway 216 that converges with thefirst polymer melt stream pathway 208 after the first polymer 104spreads out in the CD spreading manifold 210. The second polymer meltstream pathway 216 fluidly connects the second input 114 (and the firstinput 112 that is not visible) for the second polymer 106 to where thesecond polymer 106 converges with the first polymer 104 in thecoextruder 102. Once converged, the first and second polymers 104, 106pass through the land 214 and thereafter exit from the coextruder 102 toproduce the film.

FIG. 3 illustrates the die body first section 202 of the coextruder 102.For some embodiments, the second polymer melt stream pathway 216traverses through channeling 300 of a deckle rod 302 prior to passingthrough an output 304 from the deckle rod 302 subsequent to convergenceof the first and second polymers 104, 106. However, other embodimentscontemplate different arrangements for the second polymer melt streampathway 216, which may not include utilizing a ported and channeleddeckle rod.

FIG. 4 shows the coextruder 102 outputting an edge laminated film 400.In one embodiment, outputting the polymers may comprise extruding, andmore specifically, coextruding, the polymers. The film 400 includes afirst section 701 formed by the first polymer 104 bounded on each sideby second sections 702 formed of the second polymer 106, as shown inFIG. 7. Necking-in occurs at each side 402 of the film 400 causingcontraction in the CD dimensions, for example, from about 2.5 meters toabout 2.3 meters. Overall thickness of the film 400 may range from about25 micrometers to about 1.5 millimeters or be less than 2 millimeters.Due to non-Newtonian flow, the sides 402 end up thicker than a centralregion of the film 400 and are therefore unusable. Waste areas 404 ofthe film 400 result from the necking-in at the sides 402 thataccordingly requires cutting away of the waste areas 404. Discarding thewaste areas 404 without reuse of the waste areas 404 creates additionalcosts, which can be avoided or reduced if all or parts of the wasteareas are recycled (e.g., used as part or all of the second polymer 106)in the manufacture of additional film. Furthermore, material initiallyforming the waste areas 404 (i.e., the second polymer 106)advantageously includes compositions less expensive than compositions(i.e., the first polymer 104) found in the film 400 between the wasteareas 404.

For some embodiments, the first polymer 104 may include an elastomericpolymer that is relatively more elastic than the second polymer 106,which may not be elastomeric. As used herein, the terms “elastic” and“elastomeric” when referring to a fiber, sheet, film or fabric mean amaterial which upon application of a biasing force, is stretchable to astretched, biased length which is at least about 160 percent of itsrelaxed, unstretched length, and which will recover at least 55 percentof its elongation upon release of the stretching, biasing force withinabout one minute. The first polymer 104 may include, for example,elastomeric polymers that may be elastic polyesters, elasticpolyurethanes, elastic polyamides, elastic polyolefins, metallocenes andelastic A-B-A′ block copolymers, where A and A′ are the same ordifferent thermoplastic polymers, and where B is an elastomeric polymerblock, such as styrenic block copolymers.

Suitable elastomeric copolymers include ethylene vinyl acetate (EVA),ethylene-octene copolymers, and ethylene-propylene copolymers. Examplesof elastomeric polyolefins include ultra-low density elastomericpolypropylenes and polyethylenes, such as those produced by“single-site” or “metallocene” catalysis methods.

In one embodiment, the first polymer 104 is KRATON G2755™, which is ablend of poly(styrene/ethylene-butylene/styrene), a polyolefin, and atackifying resin. Any tackifier resin can be used which is compatiblewith the poly(styrene/ethylene-butylene/styrene) and can withstand thehigh processing (e.g., extrusion) temperatures. If blending materialssuch as, for example, polyolefins or extending oils are used, thetackifier resin should also be compatible with those blending materials.Hydrogenated hydrocarbon resins represent examples of tackifying resins.The first polymer 104 may include, for example, from about 20 to about99 percent by weight elastomeric polymer, from about 5 to about 40percent polyolefin and from about 5 to about 40 percent resin tackifier.For example, the first polymer 104 may include block copolymers havingthe general formula A-B-A′ where A and A′ are each a thermoplasticpolymer endblock which contains a styrenic moiety such as a poly (vinylarene) and where B is an elastomeric polymer midblock such as aconjugated diene or a lower alkene polymer. In some embodiments, thefirst polymer 104 is a blend of polyethylene (e.g., 5 melt index, MI)with the KRATON G2755™ (e.g., 70 percent 5 MI polyethylene with 30percent KRATON G2755™).

Any of a variety of thermoplastic elastomers may generally be employed,such as elastomeric polyesters, elastomeric polyurethanes, elastomericpolyamides, elastomeric copolymers, and so forth. For example, thethermoplastic elastomer may be a block copolymer having blocks of amonoalkenyl arene polymer separated by a block of a conjugated dienepolymer. Particularly suitable thermoplastic elastomers are availablefrom Kraton Polymers LLC of Houston, Tex. under the trade name KRATON®.KRATON® polymers include styrene-diene block copolymers, such asstyrene-butadiene, styrene-isoprene, styrene-butadiene-styrene, andstyrene-isoprene-styrene. KRATON® polymers also include styrene-olefinblock copolymers formed by selective hydrogenation of styrene-dieneblock copolymers. Examples of such styrene-olefin block copolymersinclude styrene-(ethylene-butylene), styrene-(ethylene-propylene),styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene. Specific KRATON® blockcopolymers include those sold under the brand names G 1652, G 1657, G1730, MD6673, and MD6973. Various suitable styrenic block copolymers aredescribed in U.S. Pat. Nos. 4,663,220, 4,323,534, 4,834,738, 5,093,422and 5,304,599, which are hereby incorporated in their entirety byreference thereto for all purposes. Other commercially available blockcopolymers include the S-EP-S elastomeric copolymers available fromKuraray Company, Ltd. of Okayama, Japan, under the trade designationSEPTON®. Still other suitable copolymers include the S-I-S and S-B-Selastomeric copolymers available from Dexco Polymers, LP of Houston,Tex. under the trade designation VECTOR™. Also suitable are polymerscomposed of an A-B-A-B tetrablock copolymer, such as discussed in U.S.Pat. No. 5,332,613 to Taylor et al., which is incorporated herein in itsentirety by reference thereto for all purposes. An example of such atetrablock copolymer is astyrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene)(“S-EP-S-EP”) block copolymer.

Other exemplary thermoplastic elastomers that may be used includepolyurethane elastomeric materials such as, for example, those availableunder the trademark ESTANE from Noveon, polyamide elastomeric materialssuch as, for example, those available under the trademark PEBAX(polyether amide) from Atofina Chemicals Inc., of Philadelphia, Pa., andpolyester elastomeric materials such as, for example, those availableunder the trade designation HYTREL from E.I. DuPont De Nemours &Company.

Furthermore, the elastic material may also contain a polyolefin, such aspolyethylene, polypropylene, blends and copolymers thereof. In oneparticular embodiment, a polyethylene is employed that is a copolymer ofethylene or propylene and an α-olefin, such as a C₃-C₂₀ α-olefin orC₃-C₁₂ α-olefin. Suitable α-olefins may be linear or branched (e.g., oneor more C₁-C₃ alkyl branches, or an aryl group). Specific examplesinclude 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene;1-pentene with one or more methyl, ethyl or propyl substituents;1-hexene with one or more methyl, ethyl or propyl substituents;1-heptene with one or more methyl, ethyl or propyl substituents;1-octene with one or more methyl, ethyl or propyl substituents; 1-nonenewith one or more methyl, ethyl or propyl substituents; ethyl, methyl ordimethyl-substituted 1-decene; 1-dodecene; and styrene. Particularlydesired α-olefin comonomers are 1-butene, 1-hexene and 1-octene. Theethylene or propylene content of such copolymers may be from about 60mole % to about 99 mole %, in some embodiments from about 80 mole % toabout 98.5 mole %, and in some embodiments, from about 87 mole % toabout 97.5 mole %. The α-olefin content may likewise range from about 1mole % to about 40 mole %, in some embodiments from about 1.5 mole % toabout 15 mole %, and in some embodiments, from about 2.5 mole % to about13 mole %.

The density of a linear olefin copolymer is a function of both thelength and amount of the α-olefin. That is, the greater the length ofthe α-olefin and the greater the amount of α-olefin present, the lowerthe density of the copolymer. Although not necessarily required, linear“plastomers” are particularly desirable in that the content of α-olefinshort chain branching content is such that the copolymer exhibits bothplastic and elastomeric characteristics—i.e., a “plastomer.” Becausepolymerization with α-olefin comonomers decreases crystallinity anddensity, the resulting plastomer normally has a density lower than thatof thermoplastic polymers (e.g., LLDPE), but approaching and/oroverlapping that of an elastomer. For example, the density of theplastomer may be about 0.91 grams per cubic centimeter (g/cm³) or less,in some embodiments from about 0.85 to about 0.89 g/cm³, and in someembodiments, from about 0.85 g/cm³ to about 0.88 g/cm³. Despite having adensity similar to elastomers, plastomers generally exhibit a higherdegree of crystallinity, are relatively non-tacky, and may be formedinto pellets that are non-adhesive and relatively free flowing.

Any of a variety of known techniques may generally be employed to formsuch polyolefins. For instance, olefin polymers may be formed using afree radical or a coordination catalyst (e.g., Ziegler-Natta).Preferably, the olefin polymer is formed from a single-site coordinationcatalyst, such as a metallocene catalyst. Such a catalyst systemproduces ethylene copolymers in which the comonomer is randomlydistributed within a molecular chain and uniformly distributed acrossthe different molecular weight fractions. Metallocene-catalyzedpolyolefins are described, for instance, in U.S. Pat. No. 5,571,619 toMcAlpin et al.; U.S. Pat. No. 5,322,728 to Davis et al.; U.S. Pat. No.5,472,775 to Obijeski et al.; U.S. Pat. No. 5,272,236 to Lai et al.; andU.S. Pat. No. 6,090,325 to Wheat, et al., which are incorporated hereinin their entirety by reference thereto for all purposes.

Particularly suitable plastomers may include ethylene-based copolymerplastomers available under the EXACT™ from ExxonMobil Chemical Companyof Houston, Tex. Other suitable polyethylene plastomers are availableunder the designation ENGAGE™ and AFFINITY™ from Dow Chemical Company ofMidland, Mich. Still other suitable ethylene polymers are available fromThe Dow Chemical Company under the designations DOWLEX™ (LLDPE) andATTANE™ (ULDPE). Other suitable ethylene polymers are described in U.S.Pat. No. 4,937,299 to Ewen et al.; U.S. Pat. No. 5,218,071 to Tsutsui etal.; U.S. Pat. No. 5,272,236 to Lai, et al.; and U.S. Pat. No. 5,278,272to Lai, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Suitable propylene-based plastomersare likewise commercially available under the designations VISTAMAXX™from ExxonMobil Chemical Co. of Houston, Tex.; FINA™ (e.g., 8573) fromAtofina Chemicals of Feluy, Belgium; TAFMER™ available from MitsuiPetrochemical Industries; and VERSIFY™ available from Dow Chemical Co.of Midland, Mich. Other examples of suitable propylene polymers aredescribed in U.S. Pat. No. 6,500,563 to Datta, et al.; U.S. Pat. No.5,539,056 to Yang. et al.; and U.S. Pat. No. 5,596,052 to Resconi, etal., which are incorporated herein in their entirety by referencethereto for all purposes.

For some embodiments, the second polymer 106 includes polyolefins, suchas one or more of polypropylene, polyethylene, ethylene copolymers,propylene copolymers, and butene copolymers polypropylene. For example,the second polymer 106 may include all or about 100 percentpolypropylene. The second polymer 106 may include a blend ofpolypropylene and the first polymer 104 (e.g., 50 percent polypropyleneand 50 percent the first polymer 104). In some embodiments, the secondpolymer 106 includes recycled material due to waste areas postlamination (shown in FIG. 5 and described further herein) due tonecking-in of an elastomeric film that is laminated between two sheetsof nonwoven materials, such as, for example, spunbonded web, meltblownweb or bonded carded web. The recycled material may include about 50percent of the nonwoven material (e.g., polypropylene) and about 50 ofthe first polymer 104.

Multiple zones of the first and second polymers can be used to providealternating regions having different functionality. For example,multiple zones of elastomeric polymer and polypropylene regions acrossfilms in some embodiments enable providing CD zones at the polypropyleneregions favorable to bonding with non-elastomeric material and that donot create inefficiency caused by bonding to the more expensiveelastomeric polymer that may thereby be rendered inelastic. For someembodiments, the term “polymer” as used herein may mean a compositionthat includes more than one polymer and/or other additives that may notbe polymeric but are included with a polymeric material to improveproperties of the composition. As an example, the first polymer 104(e.g., an elastomer impregnated with calcium carbonate) includes arelatively breathable polymer compared to the second polymer 106 (e.g.,an elastomer without calcium carbonate) once extruded into a film andactivated. For some applications, the first polymer 104 may include awettable polymer relative to a non-wettable polymer selected for thesecond polymer 106. Regardless of the purpose or subsequent use of thefirst and second polymers 104, 106 selected, the viscosity disparitybetween the first and second polymers 104, 106 at any given singletemperature would prevent edge lamination if both the first and secondpolymers 104, 106 were processed at that temperature.

FIG. 5 illustrates the coextruder outputting the edge laminated film 400that is subsequently laminated between first and second additionalmaterial layers 501, 502. For example, a spunbond material or fabricsuch as a polypropylene nonwoven may form the additional material layers501, 502 that can thereby be nonwoven fibrous layers. In operation, thefilm 400 hangs freely while being fabricated from the coextruder 102prior to introduction of the film 400 between the additional materiallayers 501, 502 and into a pair of nip or chilled rollers 504. The film400 therefore adheres in bonding contact with the additional materiallayers 501, 502. Other bonding methods can be used to adhere the film400 to the additional material layers 501, 502, such as, adhesive,thermal, hydroentangling, ultrasonic, and other methods of laminating.

In one embodiment, the additional material layers 501, 502 may be anonwoven material such as, for example, spunbonded web, meltblown web orbonded carded web. The nonwoven material refers to a structure ofindividual fibers or threads which are interlaid but not in anidentifiable pattern as in a woven fabric. Spunbond material orspunbonded web as used herein refers to facing made of small diameterfibers which are formed by extruding molten thermoplastic material asfilaments from a plurality of fine, usually circular capillaries of aspinneret with the diameter of the extruded filaments then being rapidlyreduced. Spunbond fibers are generally continuous and have averagediameter larger than about 7 microns, more particularly, between about 5and 40 microns. If the layers 501, 502 are each a web of meltblownfibers, each of the layers 501, 502 may include meltblown microfibers.The layers 501, 502 may be made of fiber forming polymers such as, forexample, polyolefins. Exemplary polyolefins include one or more ofpolypropylene, polyethylene, ethylene copolymers, propylene copolymers,and butene copolymers.

For one embodiment, one or both of the material layers 501, 502 mayinclude a multilayer material having, for example, at least one layer ofspunbonded web joined to at least one layer of meltblown web, bondedcarded web or other suitable material. A single layer of material suchas, for example, a spunbonded web having a basis weight of from about0.2 to about 10 ounces of material per square yard (osy) or a meltblownweb having a basis weight of from about 0.2 to about 8 osy, may formeach of the material layers 501, 502. In some embodiments, a compositematerial made of a mixture of two or more different fibers or a mixtureof fibers and particulates may form each of the material layers 501,502. Such mixtures may be formed by adding fibers and/or particulates tothe gas stream in which meltblown fibers are carried so that an intimateentangled commingling of meltblown fibers and other materials, e.g.,wood pulp, staple fibers and particulates such as, for example,hydrocolloid (hydrogel), occurs prior to collection of the meltblownfibers upon a collecting device to form a coherent web of randomlydispersed meltblown fibers and other materials.

When the material layers 501, 502 are each a nonwoven web of fibers, thefibers may be joined by interfiber bonding to form a coherent webstructure. Entanglement between individual meltblown fibers may producethis interfiber bonding. While fiber entangling is inherent in themeltblown process, the entangling may further be generated or increasedby processes such as, for example, hydraulic entangling orneedlepunching. For some embodiments, a bonding agent may increase thedesired bonding.

FIGS. 6 and 7 show a film exiting the coextruder 102 under two differentprocessing regimes but using the same two different polymers for thefirst polymer 104 and the second polymer 106 in both regimes. In FIG. 6,separate first and second films 601, 602 extrude from the coextruder 102with each film being mono-component based on respectively the first andsecond polymers 104, 106, which are processed without viscositymanipulation. FIG. 7 illustrates the coextruder outputting the edgelaminated film 400 made with the first polymer 104 and the secondpolymer 106 but processed with viscosity manipulation. The first polymer104 forms the first section 701 of the film 400 and is unitary instructure with the second section 702 formed of the second polymer 106and side-by-side to the first section 701.

The first section 701 defines a planar form that is continuouslyextended by the second section 702 laminated along an edge seam 703 ofthe first polymer 104 as defined by a thickness of the planar form. Thefirst polymer 104 has viscosity versus temperature curves constructedfrom at least three temperature values, as measured at shear rates of500 1/s, 1000 1/s or 1500 1/s, at least 10 percent, at least 15 percent,or at least 20 percent, different than the second polymer 106 ascalculated relative to the higher viscosity value of each of thepolymers throughout a melt temperature range of each of the polymers104, 106. Exemplary procedures for making such determinations aredescribed below as suitable test methods.

Test Methods:

Melt Temperature Range:

The Melt Temperature Range of a polymer is determined based on thedifferential scanning calorimetry (DSC) curve obtained using a standardDSC for a 5.5 mg sample of each of the polymer heated at 20° C./minutein the presence of ambient air. The first end point of the MeltTemperature Range is the temperature at the softening peak of the DSCcurve. The second end point of the Melt Temperature Range is 25° C. lessthan the temperature at the degradation peak of the DSC curve.

Melt Temperature Mid-Point:

The Melt Temperature Mid-point is the average of the melt temperaturerange end points defined above.

Viscosity (at a Particular Temperature and Shear Rate):

The viscosity is determined using a capillary rheometer (e.g., a DyniscoDual Bore Capillary Rheometer Model #LCR7000) equipped with a 1 mm dieutilizing a 10:1 length to diameter ratio and a 60° entrance angle for auser selected temperature and shear rate.

Generation of Viscosity Versus Temperature Curves at Given Shear Rates:

For each polymer, measure the viscosity at each of the end points of theMelt Temperature Range and the Melt Temperature Mid-point at shear ratesof 1/500, 1/1000, and 1/1500 1/s. For each shear rate, plot theviscosity (y axis) versus temperature (x axis) graph using linearinterpolation between the adjacent points. Include both polymers on thegraph for a given shear rate. Make a separate graph for each shear rate.Curves may also be generated for film making process shear rates.

Comparison of Viscosity Versus Temperature Curves:

Using the viscosity versus temperature charts defined above, it can bereadily determined whether there is any single temperature at which theviscosities of the two polymers are within any given percent (e.g., 10%)of one another with respect to the higher viscosity. Further, it can bereadily determined whether the viscosities of the two polymers can bematched at disparate temperatures.

EXAMPLE

In one embodiment, a film was prepared as described in relation to FIGS.1-4. A formulation of 70 percent 5 MI polyethylene and 30 percent KRATONG2755™ was introduced as a first melt stream into a coextruder. Recycledlaminate with 50 percent composition equivalent to the first melt streamand a remaining 50 percent being a spunbond grade polypropylene provideda second melt stream into the coextruder for extrusion along each sideor edge of the first melt stream. The second melt stream viscosity tomelt temperature relationship differs from the first melt stream due tothe spunbond grade polypropylene content of the second melt stream.Table 1 as follows illustrates these differences. Viscosities(pascal-second) depicted in Table 1 were determined with a Dynisco DualBore Capillary Rheometer Model #LCR7000 viscometer equipped with a 1 mmdie utilizing a 10:1 length to diameter ratio and a 60° entrance angle.

TABLE 1 Shear Rate Temperature 500 (1/s) 750 (1/s) 1000 (1/s) 1^(st)melt stream 240° C. 162 140 121 1^(st) melt stream 190° C. 300 246 207Polypropylene 190° C. 196 150 123 2^(nd) melt stream 190° C. 189 152 128

The first melt stream was introduced into the coextruder at 240° C.while the second melt stream entered the coextruder at 190° C. Thecoextruder temperature was also at 240° C. The shear rate of the streamsat output from the coextruder was calculated to be close to the 1000 1/sshown in Table 1 based on the exemplary calculation describedheretofore. A unitary edge laminated film was produced with the firstand second melt streams substantially maintaining their initialtemperature upon extrusion, as shown in FIG. 7.

For comparison, the first and second melt streams were both introducedinto the coextruder at 240° C. during another experiment. The coextrudertemperature was also at 240° C. The first melt stream separated from thesecond melt stream upon extrusion, as shown in FIG. 6.

While the invention has been described in detail with respect tospecific embodiments, it will be appreciated that those skilled in theart, upon attaining an understanding of the foregoing may readilyconceive of alterations to, variations of and equivalents to theseembodiments. Accordingly, the scope of the invention should be assessedas that of the appended claims and any equivalents thereto.

1. A method of coextruding polymers into an edge laminated film,comprising: supplying a first polymer melt stream at a first temperatureto a first inlet of a coextruder body; supplying a second polymer meltstream at a second temperature different than the first temperature to asecond inlet of the coextruder body; flowing the first and second meltstreams through first and second flow passageways passing through thebody to a converged output of the streams, wherein the first flowpassageway includes a transverse diverging chamber laterally orientedrelative to the second flow passageway at the converged output; andoutputting the converged output from the body to form the edge laminatedfilm continuous across a full width of the film.
 2. The method of claim1, wherein the coextruder body is maintained at about the firsttemperature.
 3. The method of claim 1, wherein the first melt stream ismaintained in a first portion of the width of the film and the secondmelt stream is maintained distinct from the first portion in a secondportion of the width of the film.
 4. The method of claim 1, wherein atthe converged output the first and second melt streams have atemperature differential relative to one another.
 5. The method of claim4, further comprising selecting the temperature differential wherein theviscosities of the first and second melt streams are within 10 percentof one another where outputting the converged output from the bodyoccurs.
 6. The method of claim 1, further comprising selecting melttemperatures of the first and second polymer melt streams to result inthe film being unified.
 7. The method of claim 1, further comprising:determining shear rate where the first and second polymers exit thecoextruder body; obtaining viscosity versus temperature curves for eachof the first and second polymer melt streams at the shear rate;selecting the first and second temperatures wherein viscosities of thefirst and second melt streams are within 20 percent of one another wherethe first and second polymers exit the coextruder body.
 8. The method ofclaim 1, wherein the first melt stream includes polyethylene andpoly(styrene/ethylene-butylene/styrene) and the second melt streamincludes polypropylene, polyethylene andpoly(styrene/ethylene-butylene/styrene).
 9. The method of claim 4,wherein the first melt stream includes apoly(styrene/ethylene-butylene/styrene) and about 70 percentpolyethylene and the second melt stream includes a combination ofpolyethylene and poly(styrene/ethylene-butylene/styrene) and about 50percent polypropylene.
 10. The method of claim 9, wherein the firsttemperature is about 240° C. and the second temperature is about 190° C.11. An extrusion system for coextruding polymers into edge laminatedfilms, comprising: a coextruder body having an output converged fromfirst and second flow passageways passing through the body torespectively first and second inlets, wherein the first flow passagewayincludes a transverse diverging chamber laterally oriented relative to aportion of the second flow passageway preceding the output; a first meltstream input coupled to the first inlet; and a second melt stream inputcoupled to the second inlet, wherein the second melt stream input isthermally isolated from the first melt stream input and controllable toa different temperature than the first melt stream input.
 12. Theextrusion system of claim 11, wherein a locus for convergence of thefirst and second flow passageways is beyond the transverse divergingchamber toward the output.
 13. The extrusion system of claim 11, furthercomprising a controller configured to regulate temperature of the firstmelt stream input to be at least 25° C. higher than temperature of thesecond melt stream input upon entry into the coextruder body.
 14. Anedge laminated film, comprising: a first polymer shaped in a planar formthat is continuously extended by a second polymer laminated along anedge of the first polymer as defined by a thickness of the planar form,wherein the first polymer has a viscosity versus temperature curve, asmeasured at shear rates of 500 1/s, 1000 1/s or 1500 1/s, at least 10percent different in viscosity than the second polymer at every commontemperature throughout a melt temperature range of each as calculatedrelative to the higher viscosity value of each of the polymers, theviscosity determined by a capillary rheometer equipped with a 1 mm dieutilizing a 10:1 length to diameter ratio and a 60° entrance angle, andwherein the melt temperature range for a respective one of the polymersis defined as a temperature at a softening peak of a differentialscanning calorimetry (DSC) curve to a maximum of 25° C. less than adegradation peak of the DSC curve, as determined by the DSC curveobtained for a 5.5 mg sample of the respective one of the polymersheated at 20° C./minute.
 15. The edge laminated film of claim 14,wherein the polymers have at least one matched viscosity value atdisparate temperatures throughout the melt temperature range of each ofthe polymers.
 16. The edge laminated film of claim 14, wherein the firstpolymer includes poly(styrene/ethylene-butylene/styrene).
 17. The edgelaminated film of claim 14, wherein at least about 50 percent of thefirst polymer includes polyethylene andpoly(styrene/ethylene-butylene/styrene) and the second polymer includesat least about 50 percent polypropylene.
 18. The edge laminated film ofclaim 14, wherein the first polymer is relatively more elastic than thesecond polymer.
 19. The edge laminated film of claim 14, wherein thefirst polymer is elastomeric and the second polymer is non-elastomeric.20. The edge laminated film of claim 14, wherein the first polymer isselected from the group consisting of elastic polyesters, elasticpolyurethanes, elastic polyamides, elastic polyolefins, metallocenes andelastic A-B-A′ block copolymers, where A and A′ are the same ordifferent thermoplastic polymers, and where B is an elastomeric polymerblock.
 21. The edge laminated film of claim 14, wherein the first andsecond polymers are disposed between first and second additionalmaterial layers laminated to respectively first and second faces of theplanar form.
 22. The edge laminated film of claim 21, wherein the firstand second additional material layers are each nonwoven fibrous layers.23. The edge laminated film of claim 21, wherein the first and secondadditional material layers are each spunbonded polypropylene materials.24. The edge laminated film of claim 14, wherein the second polymer isdirectly laminated without intervening adhesive along the edge of thefirst polymer.